The importance of research context and level has been increasingly recognized, which breeds the demand of a robust grand theory that can systematically integrate the cross-level constructs. Action theory, developed by Talcott Parsons (1902-1979), treats all social phenomena that contain actors, goals, situation and normative orientations as actions and uses different systems to explain the interactions among them, thus offering a very good grand theoretical framework to satisfy the growing need in OB research. In action theory, Parsons uses action unit and action system (personality system, social system and cultural system) to integrate the key factors of social action and the interaction between different levels of action system. The theoretical framework can systematically integrate individual, group and society level phenomena. Also, because action theory argues that values are the most important factor that actors use when making choices about modes, means and goals, the theory also lays a very good foundation for value-based leadership study. Using leadership theory as an example, this article exemplifies how action theory can be applied to OB research.